Typically in the prior art one has to open a folding knife by grabbing the outer surface of a blade of the knife and pulling and/or rotating the blade out of a housing. There are also switchblade knives which are known which allow one to press a single button, and in response a blade immediately springs out from a fully closed position within a housing to a fully opened position outside of the particular housing.
U.S. Pat. No. 4,974,323 to Cassady discloses a folding knife which can be opened by applying finger pressure to a stem portion 30. (Cassady, FIGS. 10–15; col. 5, Ins. 65-col. 8, In. 3). The stem portion 30 is attached to a control plate 28 which can move within a cavity 52 of an engagement plate 50. The control plate 28 is attached to a crankpin 24 which can move within an arcuate crankpin slot 48. The crankpin 24 is attached to a knife 20. (Cassady, FIG. 3, col. 4, Ins. 55–65).
In Cassady, in order to move the knife 20 from a fully closed position (Cassady, FIG. 10) to a fully opened position (Cassady, FIG. 14 or 15), finger pressure is applied to the stem portion 30 first in an easterly and southerly direction, until the heal 38 and toe 34 of the plate 28 are in a bypass slot 56 (FIG. 13, partially opened position) and thereafter in a westerly and northerly direction until the heal 38 and toe 34 of the plate 28 are outside the slot 56. (Cassady, FIG. 14 or FIG. 15; col. 5, Ins. 65-col. 8, In. 3) The requirement that an operator move the plate 28 in multiple and opposing directions in order to operate the Cassady device, makes the device cumbersome to operate.